Video signals are transmitted between a video transmission source and a video receiving unit in a video intercommunication system as a representative stream of digital data bits known as a compressed or encoded bit stream. A video encoder in the transmission source is utilized for encoding a video signal using a specified video transmission standard. The video transmission standard defines the spatial and temporal resolution, such as the image resolution and the image frame rate, respectively, used for encoding a video signal. A video decoder in the receiving unit decodes or decompresses the compressed bit stream back into video signal form.
Advances in video transmission technology have led to the development of video encoding and video decoding equipment which may be configured to operate using a variety of video transmission standards. The video receiving equipment which includes a video decoder, however, can only decode a compressed bit stream that it receives which is encoded using the same video transmission standard as that which the video decoder is configured to perform decoding. The high likelihood that video signals encoded using a first video transmission standard will be received at video decoding equipment configured to operate using a video transmission standard other than the first video transmission standard establishes a need for an economical and efficient method for converting a first compressed bit stream encoded using a first video transmission standard to a second compressed bit stream encoded using a second video transmission standard.
A standard approach is to convert a first compressed bit stream back to video signal form, and then to utilize an additional video encoder, which is configured to encode video signals using the second video transmission standard, as part of the video decoding equipment, for converting the video signal to a second compressed bit stream. The use of the additional video encoder, however, enormously increases the cost of the video decoding equipment, such as a television set, that includes the video decoder utilized for displaying a video signal. The additional video encoder also increases the cost of video transmissions in terms of processing time.
Further, the use of a video encoder for converting between compressed bit streams encoded at different video transmission standards fails to compensate efficiently for possible differences in the encoded parameters of a video signal which are a function of the video transmission standard. For instance, a high image resolution video encoder cannot compensate for the fact that the video signal it is re-compressing may have been initially encoded by a video encoder configured to operate using a video transmission standard having a lower image resolution.